Self-Inflating Screening Shield, in Particular Umbrella

ABSTRACT

A self-inflating screening shield, in particular umbrella, has an inflatable envelope ( 11 ) made of a flexible material. The interior of the envelope ( 11 ) is evacuated prior to use, and by means of a chemical reaction a gaseous substance can be produced therein with which the interior of the envelope ( 11 ) is inflated. The chemical reaction may consist in dissolving a sodium (bi)carbonate granulate in citric acid. The citric acid may be accommodated in a container which is made to rupture by pressure being applied externally to the envelope ( 11 ) by a user, for example at a predetermined breaking point, or by being torn at a predetermined tearing point, thus triggering the chemical reaction. A self-inflating balloon can also be produced in this way.

The present invention relates to a self-inflating screening shield, inparticular umbrella, according to the preamble of claim 1. The inventionalso relates to a self-inflating balloon according to the features ofclaim 10.

Conventional umbrellas in everyday use are generally relatively bulkydevices that are often inconvenient to handle. They are annoyingparticularly when they are not being used, i.e. as long as theanticipated rain has not yet started, or when it has stopped raining. Inaddition, they are often left behind or forgotten, due to the very factthat they are not easily transportable. This, in turn, often leads tothem not being taken when no rain is expected. If it starts to rainafter all, one is largely unprotected, or tries to protect oneselfagainst the rain in a makeshift manner by holding items such as bags, orarticles of clothing such as jackets and the like, over one's head, butwith the consequence that these items and clothing articles are damaged.

Since this basic problem has long been known, partly telescopingumbrellas were designed a long time ago that require substantially lessspace when closed than is the case with conventional umbrellas, butwhich are still relatively large and bulky. Although it is possible toaccommodate these in a bag or the like that one is carrying, theconsiderable weight of such umbrellas is annoyingly noticeable. If thereis no intention to carry a bag, umbrellas of the latter kind arelikewise impracticable to transport.

The problems outlined in the foregoing are further exacerbated by thefact that changes in global climate conditions could lead to localweather conditions changing more quickly from one extreme to the other.Within a few hours or an even shorter period of time, the weathersituation and particularly the likelihood of rain can therefore changein a fundamental way. This gives rise to a need to be able to protectoneself against sudden rain showers in effectively any outdoorsituation.

It can be seen from the published prior art that one aim in improvingthe ease of handling of umbrellas is to reduce their bulkiness, i.e. todecrease the number and/or size of bulky parts in umbrellas. Thebulkiness of conventional umbrellas is due, in particular, to the handlemember, the central support rod and the radial struts which tension thescreening material. One aim of further developments must therefore be toreplace these elements with other elements that functionally areapproximately equivalent.

In a number of documents, it has therefore been proposed to configure anumbrella as an inflatable umbrella that is inflated for use and canotherwise be transported in a practicable manner in a folded-togetherform. A gas-filled envelope replaces the screening material commonlytensioned by metal struts, thus ensuring the necessary stiffness.

Document DE 20 2004 002 172 U1 describes an umbrella or sunshade whichis provided with an inflatable umbrella- or disk-shaped air chambercoupled to a compressed air cartridge. By means of a valve which can beactuated by a push-button, it is possible to control the supply of airfrom the cartridge to the air chamber. When the umbrella or sunshade isno longer needed, the air is released from the air chamber by means ofthe valve and the umbrella or sunshade is folded up and stowed in acase.

In document U.S. Pat. No. 3,889,700, a compact, self-inflating umbrellafor once-only use is proposed. The umbrella is provided with a case, thebottom portion of which serves as a handle member when using theumbrella. Inside the case, near the bottom thereof, a pressure vesselfilled with a pressurised boiling liquid is disposed. Above said vessel,the inflatable shielding screen is stowed away in a folded state insidethe case. When in use, a closure element of the pressure vessel isbroken away by external mechanical action so that the liquid escapesthrough the opening thus produced, expands thereby and is guided as agaseous substance into the inflatable chambers of the screening shield.As a result of the air chambers being inflated, the screening shield ispressed out of the upper part of the case and unfolds to its full size.The umbrella is thrown away after one use.

For several reasons, these different approaches to solving theaforementioned problem have not been able to establish themselves bywidespread use. Firstly, the proposed umbrellas include bulky elementssuch as handle members, cases or gas production devices, with the resultthat, in the unopened state, they are still too bulky and require toomuch space. In other words, a decisive technical advance compared tostandard telescoping pocket umbrellas cannot be achieved with suchapproaches. Secondly, the gas production devices provided in them forinflating the screening shield are too complex in design and tooexpensive to produce, with the consequence that inflatable umbrellasproduced in this manner, especially those for once-only use, can not beoffered at an attractive price.

The object of the present invention is therefore to specify aself-inflating umbrella which is space-saving when not in use and whichcan also be produced with less production effort. The object of thepresent invention, more particularly, is to define a self-inflatingumbrella which essentially no longer contains any bulky elements.

These objects are achieved by the feature of the characterising portionof claim 1. Advantageous developments and configurations of theinvention are described in subclaims.

A self-inflating screening shield according to the present inventioncomprises an inflatable envelope made of flexible material, wherein agaseous substance can be produced inside the envelope by means of achemical reaction. In one embodiment, said screening shield is anumbrella. In another embodiment, said screening shield is a sunshade.

The present invention thus proceeds from the basic realisation that thedevices proposed in the published prior art for providing or producing agas for inflating the shielding envelope are invariably too voluminousin design and therefore too bulky, since the medium to be used forinflation must be enclosed in a pressure-tight container when not inuse, be it in the form of a compressed air cartridge or a pressurisedboiling liquid enclosed in a container.

One essential idea of the present invention is therefore to provide thegaseous substance for inflating the umbrella in some other manner thatobviates the need to use bulky containers. This is made possible by thepresent invention.

The inventive idea provides the basis for storing certain startingsubstances, with the aid of which the gaseous substance is to beproduced, without using rigid pressure vessels as storage. Anotheradvantage is that individual chambers can be separately filled with gasby means of said starting substances. More particularly, two or morechemical substances can be disposed, as starting substances for thechemical reaction, spatially separate from each other inside theenvelope, and the chemical reaction can be triggered, in case of use, bythe chemical starting substances being brought into contact with eachother. This basically obviates the need for the chemical startingsubstances to be accommodated in rigid, pressure-tight containers. It isnot even necessary, in essence, for them to be accommodated incontainers at all when in their initial state.

However, one exemplary and advantageous embodiment provides that atleast one of the chemical substances is accommodated in a containerwhich can be opened externally by the effect of pressure, such that thechemical substance contained therein is released and can come intocontact with the respective other chemical substance. For example, itcan then be arranged that the container is disposed at a definedposition inside the envelope, and that a marking is applied at alocation on the outer wall of the envelope which is closest to saidposition. The marking, which may also be configured as a predeterminedbreaking point, serves to indicate to the user that the marked place bepressed in case of use, thus opening the container by the effect ofpressure. The container may be provided, for example, with a flexibleouter skin, so that the container can be made to rupture by the effectof mechanical pressure, and the chemical substance contained therein canescape. In another embodiment, the container may be configured in such away that it is opened by tensile force.

In one embodiment, a plurality of separate air chambers are provided,and each air chamber is filled with air by means of a chemical reactionspecific to that chamber. In one embodiment there are two such chambers,in another embodiment three chambers, in another embodiment fourchambers and in yet another embodiment five chambers. In one embodiment,the shielding screen is filled with one chamber, while the handle isfilled with a separate chamber. In this way, the user can firstly openthe shielding screen by means of a first reaction, and then “open” thehandle by triggering a second reaction. In another embodiment, theshielding screen is only partially fitted with air chambers, withmaterial, for example, being provided between the chambers. In oneembodiment, the chambers are located where the frame for opening theshielding screen is normally located. This means that the chambers areattached in a star-shaped formation in such a way that the shieldingscreen is opened between them. The chambers can also be filled with gasseparately in this way, with each chamber then being assigned a specificmixture of chemicals. This advantage is absent from the prior art, sincea plurality of pressure cartridges cannot be used.

With regard to the starting substances for the chemical reaction, afirst chemical substance may contain or consist of a solid, and a secondchemical substance may contain or consist of a liquid, and when thesubstances come into contact, the chemical reaction may consist in thesolid being dissolved by the liquid, with the gaseous substance beingone of the reaction products. In one practical embodiment, the solid maycontain or consist of sodium carbonate (washing soda) or sodiumbicarbonate (baking soda), and the second chemical substance maycomprise an acid. When said solids are dissolved in the acid, gaseousCO₂ is produced as the reaction product. Citric acid, practicably as aningredient of lemon juice, or tartaric acid may be used as the acid.

As an alternative to the choice of material proposed above for the firstand second chemical substance, a different solid which can be dissolvedin a liquid may be chosen for the first chemical substance such that agaseous substance such as CO₂ or O₂ is released when the solid isdissolved in the liquid. For example, the solid may also be provided bya kind of effervescent powder, and the liquid in the simplest case bywater, so that the desired result of a chemical reaction, with theformation of a gaseous substance, can likewise be achieved.

The solid should preferably be present in the form of a powder orgranulate, so that it has as much free surface exposed to the liquid aspossible.

In one preferred embodiment, bulk sodium bicarbonate, preferably in thecrystal phase (e.g. 4.88 g (58 mmol)), and a solution of citric acid andwater, preferably 3.78 g (19.7 mmol) citric acid and 16 ml water, whichis e.g. sealed into a thin plastic bag (e.g. 6×6 cm format), areprovided in the loop which is configured as a carrying handle. Theaforementioned quantities produce 1.3 litres in volume of gas, which, ina shielding screen with a volume of 1 litre, produces the slight 0.3 barof overpressure necessary to unfold said shielding screen.

In general, X=V(p+Δp)/22.4;

where X is the number of mols (of gas/acid/base)

-   -   V is the volume [in litres] of the shielding screen    -   p is the ambient pressure (1 bar)    -   and Δp is the overpressure [in bar]

In the case of polybasic acids (e.g. citric acid), the number of mols Xmust be divided by the basicity (in the case of citric acid: 3). Thesame principle applies accordingly in the case of bases.

The advantage is that the combination of substances can be stored inthis form without limits, which is important particularly in the case ofa disposable shielding screen. When in use, the plastic bag ispreferably made to rupture by applying pressure, for example by afinger, and the formation of CO₂ occurs without further extrinsicaction, thus making the screening shield unfold. A kind of ripcord whichopens the bag of liquid may also be attached.

In one particularly preferred embodiment, the following reaction iscarried out:

3 NaHCO₃+C₆H₈O₇=3 CO₂+C₆H₅O₇Na₃+3H₂O

in words:

sodium bicarbonate+citric acid=carbon dioxide+sodium citrate+water

Sodium bicarbonate is preferred because it is twice as effective assodium carbonate. Furthermore, it is safer and more environmentallyfriendly because it is not as strongly alkaline as sodium carbonate.

Other possible acids are malic acid, tartaric acid, succinic acid,amidosulphonic acid or fumaric acid, for example. The criterion forselection is the lowest possible level within the classification ofhazardous substances. The aforementioned acids, including citric acid,are classified as “irritant”, whereas acetic acid, for example, is“corrosive”. A low classification as hazardous substance isadvantageous. An acid classified as “irritant” is therefore preferred.

The overpressure Δp in the chamber is preferably more than 0.1 bar, morepreferably between 0.1 and 2 bar, even more preferably between 0.2 and 1bar, and especially preferably between 0.3 and 0.5 bar. A higherpressure may be used in the case of stronger material.

In one preferred embodiment, coloured substances or dyes are carried bythe gas (CO₂) which propagates in the screening shield, said colouredsubstances or dyes being fluorescent or phosphorescent, or made to glowin some other way.

A handle member in the form of a flexible loop may also be provided at aposition on the outer wall of the envelope.

With the present invention and, where relevant, with the developmentsand embodiments specified in the foregoing, it is possible for theself-inflating screening shield to be folded together in its initialstate to a very space-saving size, since it no longer has any bulky,space-consuming parts.

In the folded-together form, a self-inflating screening shield can becarried easily in a jacket or trouser pocket. When needed, it can beactivated by applying pressure is to the marking on the outer skin ofthe envelope so that the chemical reaction is initiated inside it. Dueto the vacuum inside the envelope or inside the chambers to be inflated,when in the initial state, the gaseous substance produced by thechemical reaction flows very rapidly into the envelope or chambers andthus inflates these very quickly, with the result that the screeningshield or umbrella is available within a very short period of time.Since the screening shield is envisaged for once-only use, it may bethrown away as soon as it is no longer needed. After use, the chemicalsused to inflate the screening shield are absolutely non-hazardous, areneutral in water, do not pose a hazard for water resources and arebiodegradable.

In one embodiment, a material such as that used in vehicle airbags isused. The air chambers may have threads or transversal connectors on theinside. The upper and lower sides may be connected, or the lateralsides. The air chamber may be bowl-shaped. A water-repellent material ispreferred. The screening shield may also have a double-walledconstruction. Parts of the screening shield may comprise carbonnanotubes. These may be embedded in the screening shield material.Kevlar fibres may also be used.

Polyethylene terephthalate (PET) is also a preferred material. Apolyethylene terephthalate polyester film (BOPET: biaxially orientedpolyethylene terephthalate) such as Mylar® is particularly preferred.Mylar® is characterised above all by its high tensile strength, chemicalresistance, plastic stability and translucency or transparency, and isan electrical insulator. These properties are advantageous for theinventive screening shield.

The screening shield is made by sewing, welding or glueing, for example.Air-tightness is important both for the selection of material and forproduction.

Seams and material must be chosen such that they withstand the pressureof the gas volume and no gas escapes.

In addition, the handle may be connected to the screening shield bythreads. The preferred connection is one which provides the longest pathbetween the outer edge of the screening shield and the handle. A radialdistribution is preferred.

The material of the screening shield may be coloured or transparent. Itcan also be phosphorescent or fluorescent. The material of the screeningshield may have a signal colour.

In one embodiment, the screening shield has an edge which prevents waterfrom flowing under the screening shield. In another embodiment, an airchamber forming a bulge is provided in the shape of a circle around theedge of the screening shield.

In one embodiment, the chambers which hold the chemicals havepredetermined breaking points. If the chemicals are in bags, said bagsmay have perforations. One particularly preferred embodiment is one inwhich the screening shield is rod-shaped when in the folded-togetherstate. In this case, the predetermined breaking point is preferablyprovided in the middle of the rod so that the chemical reaction istriggered by simply pressing against the predetermined breaking point ofthe rod or breaking the same.

In one embodiment, the material of the screening shield is folded usingthe origami technique after it has been glued or welded.

In one particularly preferred embodiment, the material of the screeningshield is itself biodegradable.

EXAMPLES

The invention shall now be described in greater detail with reference toembodiments and to the drawings, in which:

FIG. 1 shows a perspective view (seen at an angle from above) of a firstembodiment of a self-inflating screening shield or umbrella in theinflated state;

FIG. 2 shows a perspective view (from below) of the first embodiment asshown in FIG. 1;

FIG. 3 shows a cross-sectional view of a central chamber of the envelopeof the self-inflating umbrella;

FIG. 4 shows a plan view of the folded-together umbrella, with theuppermost located central chamber; and

FIG. 5 shows a perspective view (seen at an angle from above) of asecond embodiment of a self-inflating umbrella according to theinvention.

FIG. 1 shows a perspective view from above of a first embodiment of aself-inflating umbrella according to the invention. The self-inflatingumbrella 10 essentially comprises an inflatable envelope 11 made of aflexible material, for example of a suitable plastic material such aspolypropylene or the like. A suitable film material may also be used, asan alternative. When not in use, i.e. prior to inflation, there is avacuum inside envelope 11, so it can be folded together into a verysmall space. Envelope 11 is produced in such a way that, when inflated,it adopts the shape of a dome as shown in FIG. 1, which can be heldabove one's head as a protection against rain. In the perspective viewseen at an angle from below as shown in FIG. 2, it can be seen that aloop 13 made of a flexible material is attached to a central portion onthe concave side of the dome, through which loop a hand can be placedwhen in use, so that the umbrella 10 can be held securely and reliablyabove the carrier's head. The umbrella 10 can be produced in differentsizes. In the smallest embodiment, the diameter of the dome is justlarge enough for the head of the user to be covered. In somewhat largerembodiments, the dome can have a diameter of such size that the shoulderarea of the user is covered as well. Envelope 11 may contain a centralchamber 12 which may be of circular shape when viewed from above and thedimensions and boundaries of which may be visible to the outside.Production of the gaseous substance for activating and inflatingumbrella 10 occurs in the central chamber 12.

In FIGS. 3 and 4, the central chamber 12 is shown in cross-section andin a plan view, respectively. Inside chamber 12, a container 12.2containing citric acid or lemon juice is attached to a bottom surface12.1. Laterally adjacent to container 12.2, a granulate or powder 12.3consisting of washing soda (sodium carbonate) or baking soda (sodiumbicarbonate) is disposed. A marking 12.4 is applied to the outer convexside of envelope 11. The outer wall of envelope 11 can be pressed in atthis marking as far as container 12.2, such that container 12.2 can becompressed and made to rupture. As an alternative to marking 12.4, theouter skin of envelope 11 may be either wholly transparent, ortransparent only in the region of central chamber 12, so that the usercan visually perceive container 12.2 and can also observe the gasproduction process after container 12.2 has been forced to rupture.

Container 12.2 may consist of a small envelope or bag shaped out ofplastic and filled with citric acid or lemon juice, which is square inshape and welded together at one or several of its lateral boundaries.When compressed, the envelope preferably tears at one or several ofthese seams. As is shown in FIG. 4, suitable precautions can be taken sothat container 12.2 ruptures on one side only and hence its contentsescape in one direction only, namely in the direction of the granulate12.3. As shown, container 12.2 may be additionally reinforced at threelateral boundaries and connected to the floor side 12.1. Whencompressed, container 12.2 thus ruptures only on the left side. There aproduction-related seam may be located, or a predetermined breakingpoint, such as a perforation or the like, may be alternatively oradditionally provided in the outer skin of container 12.2.

After container 12.2 has ruptured, the liquid contained therein escapesrapidly because of the vacuum inside central chamber 12 and theremaining interior of envelope 11. However, it has to be ensured thatthe lemon juice flows over granulate 12.3 in a directed manner and ascompletely as possible in order to bring about the chemical reaction,i.e. the dissolution of the sodium (bi)carbonate granulate 12.3. Thiscan be achieved e.g. by covering the space in container 12.2 and thesodium (bi)carbonate granulate 12.3 by means of a membrane 12.5. Saidmembrane 12.5 consists of a material which is permeable to the gaseoussubstance produced by the chemical reaction, i.e. gaseous CO₂ in thepresent embodiment, or it is provided alternatively with a dense networkof pores through which only the gaseous substance can pass. Thus, it isensured that neither the granulate 12.3 can enter chamber 12 and theremaining interior of envelope 11 before the umbrella 10 is put into usenor, after container 12.2 has been forced to rupture, the liquid is ableto escape without coming into contact with the granulate 12.3. To thisend, the liquid may have a surface tension which ensures that it cannotpass through the pores of membrane 12.5.

In the chosen embodiment, the granulate consists of washing soda, i.e.sodium carbonate with the chemical formula Na₂CO₃, or of baking soda,i.e. sodium bicarbonate with the chemical formula NaHCO₃. In the presentembodiment, the acid used to dissolve the sodium (bi)carbonate granulateis citric acid with the chemical formula C₆H₈O₇. Lemon juice contains5-7% citric acid, so it is possible in the simplest case for container12.2 to contain lemon juice. Gaseous CO₂ is produced as a reactionproduct when the sodium (bi)carbonate granulate is dissolved in citricacid. The equation for this chemical reaction is the following:

3 Na₂CO₃+2 C₆H₈O₇=3H₂O+3 CO₂+2 C₆H₅O₇Na₃

or, expressed in words:

sodium carbonate+citric acid=water+carbon dioxide+sodium citrate

However, it is also possible for a different acid, for example tartaricacid, malic acid, succinic acid, amidosulphonic acid or fumaric acid, tobe used to dissolve the granulate.

The gaseous CO₂ thus produced escapes very rapidly through the pores ofmembrane 12.5 into chamber 12 and from there into the remaining interiorof envelope 11, thus inflating envelope 11. The base portion of envelope11 may have a slightly greater thickness in the region of the centralchamber 12 than the rest of the outer skin of envelope 11, in order toensure the requisite stability and strength in said region. As shown inFIG. 3, loop 13 made of flexible material is externally attached to saidbase portion. Loop 13 preferably consists of a thin, space-saving layerof a suitable plastic material such as polypropylene. The outer edge ofenvelope 11 is also shown in FIG. 3. As can be seen, an upper envelopeportion 11.1 can be welded together in this region with a lower envelopeportion 11.2 along a circumferential seam 11.3.

FIG. 4 is simultaneously a plan view of the folded-together screeningshield. During manufacture, the product is folded in such a way that thedepicted square around the central chamber 12 results, wherein envelope11 and loop 13 are folded together in a suitable manner in an imageplane behind the square shown, and are connected to said square. Theiractual proportions can correspond approximately to those shown in FIGS.3 and 4. The square pack can therefore be easily carried in a pocket ofan article of clothing. If desired, however, the square pack can be keptin an adapted case, in particular to avoid the screening shield beingunintentionally triggered.

FIG. 5 shows a perspective view, seen at an angle from above, of asecond embodiment of a self-inflating umbrella according to theinvention. Unlike the first embodiment shown in FIG. 1, theself-inflating umbrella 20 has an envelope 21 which is provided with anumber of inflatable channels 21.1 projecting radially from a centralchamber 22, between which channels single-layered regions 21.2 notshaped as envelopes extend. Although an umbrella 20 of this kind issomewhat more complicated to manufacture, it can be inflated morequickly when used, because only channels 21.1 and hence less volume needto be filled with the gaseous substance that is produced. Chamber 22 hassubstantially the exact same shape as chamber 12 in FIGS. 3 and 4 of thefirst embodiment. The view shown in FIG. 3 can also serve as across-sectional view through the umbrella 20 in FIG. 5, whereincross-section is through chamber 22 and two channels 21.1 extendingtherefrom.

Instead of seven channels 21.1, as shown in FIG. 5, more channels orless channels, for example only two or three channels, may also be used.

After one use, the self-inflating umbrella of the present invention canbe thrown away. Environmentally friendly materials are thereforepreferred.

The invention relates also to a self-inflating balloon in which the sameprinciple is applied as in the umbrella described above, and in whichall the other details and features can be applied as described above inconnection with the self-inflating umbrella. For example, a simple toyballoon can be made, particularly in the form of a foil balloon made ofa foil material, inside which there is a vacuum prior to use. Acontainer filled with an acid such as citric acid can be disposed insidesuch a balloon, and a solid such as a sodium (bi)carbonate granulate canbe disposed outside it. The container can be secured at a certain placeinside the envelope, as described in the foregoing, and be suitablymarked on the outside. However, the container can also be freely movableinside the envelope. If the balloon is small enough, it is possible tofeel from the outside where the container is located. The sodium(bi)carbonate granulate can likewise be fixed at a certain place on theinside of the envelope, as described in the foregoing, or alternativelycan be disposed in a freely moveable manner inside the envelope. If theballoon is small enough, the granulate will be covered almost completelyby the liquid in such a case also. By pressing the outer skin of theballoon at a suitable place, the container can be made to rupture suchthat the balloon is inflated by the gas formed by the chemical reaction.

In the simplest embodiment, the balloon may comprise two parts, inparticular foils, which are welded to each other at their respectivecircumferential rims and form a closed envelope in such a way that theenvelope is filled with the container and the granulate and a vacuumotherwise prevails inside. The two foils are congruent with each other,i.e. they can be laid on top of each other in a perfect overlap. Wheninflated, the foils can also produce a figure such as an animal or thelike. In the simplest case, the foils can also be circular in shape, sothat the inflated balloon is shaped substantially like a ball or globe.The balloon can also be used as an advertising medium by printing anadvertising message on the outer surface of the envelope.

1. A self-inflating screening shield comprising an inflatable envelope(11) made of flexible material, wherein a gaseous substance can beproduced inside the envelope (11) by means of a chemical reaction.
 2. Aself-inflating screening shield according to claim 1, wherein two ormore chemical substances are disposed spatially separate from each otherinside the envelope (11) and the chemical reaction can be triggered bythe chemical substances being brought into contact with each other.
 3. Aself-inflating screening shield according to claim 2, wherein at leastone of the chemical substances is accommodated in a container (12.2)which can be opened by the effect of pressure or tensile force.
 4. Aself-inflating screening shield according to claim 2, wherein a firstchemical substance contains or consists of a solid, a second chemicalsubstance contains or consists of a liquid and the solid can bedissolved by the liquid, wherein the gaseous substance is one of theresultant reaction products.
 5. A self-inflating screening shieldaccording to claim 4, wherein the first chemical substance is sodiumcarbonate or sodium bicarbonate and the second chemical substancecomprises an acid, such that the reaction product resulting from thechemical reaction is gaseous CO2.
 6. A self-inflating screening shieldaccording to claim 5, wherein the second chemical substance contains orconsists of citric acid.
 7. A self-inflating screening shield accordingto claim 3, wherein the container (12.2) is disposed at a definedposition inside the envelope (11) and a marking (12.4) is applied at alocation on the outer wall of the envelope (11) which is closest to saidposition.
 8. A self-inflating screening shield according to claim 3,wherein the container (12.2) has a predetermined breaking point and/or apredetermined tearing point.
 9. A self-inflating screening shieldaccording to claim 7, wherein a handle member (13) in the form of aflexible loop is attached at a position on the outer wall of theenvelope (11).
 10. A self-inflating screening shield according to claim1, wherein the screening shield is an umbrella.